Rhodosciadium diffusum (Coult. & Rose) Mathias & Constance

Rhodosciadium diffusum (Coult. & Rose) Math. & Const Bull. Torrey Club 68: 124. 1941.
Deanea diffusa Coult. & Rose, Proc. Wash. Acad. 1: 155. 1900.
Stout, 15-25 dm. high, glaucous throughout, the foliage often scaberulous; leaves deltoid in general outline, excluding the petioles 20-30 cm. long, ternate-bipinnate, the leaflets ovate, acute at the apex, truncate to cuneate at the base, distinct or the terminal confluent, sessile to petiolulate, 2.5-3.5 cm. long, 2-2.5 cm. broad, deeply incised or divided, minutely scaberulous on the veins beneath or glabrate; petioles stout, 10 cm. or more long, somewhat inflated; inflorescence terminal with a continuous axis bearing usually opposite or occasionally whorled branches or peduncles, some of which are trifurcate or irregularly branched, the peduncles slender, 1.5-3.5 cm. long, each subtended by a small bract, the lateral umbels usually sterile; involucre wanting; involucel of 1-several linear to lanceolate bractlets 2-10 mm. long, shorter or longer than the flowers and fruit; rays 2-5, spreading to spreading-ascending, 1.5-2 cm. long; pedicels 1-2, spreading-ascending, 3-5 mm. long; petals greenish-yellow to purple; fruit oval, a little narrowed toward the rounded apex, cordate at the base, 8-15 mm. long, 6-10 mm. broad, the dorsal ribs prominent, the lateral wings once to twice as broad as the body ; seed-face slightly concave.
Type locality: "On lava beds near Cuernavaca," Morelos, Pringle 7177.
Distribution: Mexico and Morelos to Chiapas (Hinton 8099, Matuda 1623, Pringle 8425).